Desulphurisation of such feedstocks can be effected by passing the gas through a suitable absorbent which is commonly zinc oxide and/or copper oxide and is typically in the form of granules or pellets.
When a feedstock containing absorbable sulphur compounds such as hydrogen sulphide is passed through a bed absorbent, break-through of the sulphur compounds into the effluent occurs long before the bed has reached its theoretical absorption capacity, i.e. where all of the absorbent in the bed is fully saturated, because, while the absorbent near to the bed inlet may become fully, or nearly fully, saturated with the sulphur compounds, break-through occurs well before the absorbent at the bed outlet becomes saturated.
This early break-through is particularly noticeable where the absorption temperature is low. Recently absorbents having a high surface area, typically above 20, and particularly in the range 50 to 200, m.sup.2 g.sup.-1 have become available and are of particular use for low temperature desulphurisation, e.g. at temperatures between -10.degree. C. and 200.degree. C. Even so premature breakthrough is a problem.